A conventional stacker crane is disclosed in Japanese Patent Preliminarily Publication No. 2003-212308, where an upper frame comprises a pair of left and right frame portions. These frame portions are constituted of a pair of front and rear connecting plates, which are connected to the front and rear support rods, respectively, by bolts, and an elongated upper frame portion extended in the front and rear direction of the crane and being connected to the pair of front and rear connecting plates at both ends thereof. The pair of left and right frame portions are connected to the front and rear support rods, respectively, such that the rods are positioned between the left and right frame portions.
Each connecting plate is protruded in an upward direction more than the rods, and the protruded portion of the connecting plate has an engagement portion having a reversed C-shape viewed from the front and rear direction of the crane. The upper frame portion comprises a frame member having a reversed C-shaped cross section and is connected to the connecting plates by bolts in a condition in which the end portions of the upper frame portion in the front and rear direction of the crane are engaged to the engagement portions of the connecting plates, respectively. That is to say, an engagement portion is formed with the connecting plate, to which the upper frame portion is connected by bolts in a condition that the upper frame portion is engaged into the engagement portion of the connecting plate, so that the up-and-down fluctuation of the upper frame portion against the connecting plate can be suitably controlled. Thereby, the pair of front and rear support rods are appropriately connected to the upper and lower frames in a condition that the lower frame, the front and rear support rods, and the upper frame are assembled together forming a frame body having a rectangular shape viewed from side. As such, for instance, a deformation from the rectangular-shaped assembling condition caused by the fluctuation of the parallel-arranged front and rear support rods in the back and forth direction against the lower frame is suitably prevented.
According to the conventional stacker crane disclosed in Japanese Patent Preliminarily Publication No. 2003-212308, the upper frames of the left and right frame portions are connected to each other via the connecting plate, to which the upper frame portions are fit at many points in the back and forth direction of the crane, by bolts, so that the upper frame is constituted as a ladder-shaped frame, which is hard to be deformed as a whole. In the conventional stacker crane disclosed in Japanese Patent Preliminarily Publication No. 2003-212308, a pair of front and rear attachment plates for supporting front and rear guide rollers, respectively (which are being urged against the side surface of a guide rail provided on the ceiling side), are connected to the connecting plate by bolts in a condition that the attachment plates are mounted on the left and right connecting plates, between which the front support rod is held, or mounted on the left and right connecting plates, between which the rear support rod is held.
The upper frame of the conventional stacker crane is constructed so that an engagement portion, which engages the upper frame portion, is formed in the pair of front and rear connecting plates, which are connected to the front and rear support rods by bolts, respectively, and the connecting plate and the upper frame portion are connected to each other by bolts in a condition that the upper frame portion is being engaged into the engagement portion. This, therefore, shows the tendency for the steps for the upper frame production to become complex due to the facts that the shape of the connecting plates is complex. An improvement to this has been long awaited.
Furthermore, the conventional stacker crane is constituted such that the relative movement of the connecting plate and the upper frame portion in the front and rear direction of the crane is restricted due to friction caused by the bolt connection therebetween and, therefore, the connecting strength between the connecting plate and the upper frame in the front and rear direction of the crane is insufficient. As a result, the connecting strength for connecting the front and rear support rods in the front and rear direction of the crane, such as the strength for restricting the movement of the front and rear support rods to the direction that the rods are spaced from each other, becomes insufficient. An improvement from this point of view has also been awaited.
In fact, the production of the upper frame of the conventional stacker crane tends to be cumbersome, and the strength for connecting the front and rear support rods in the front and rear direction of the crane is apt to be insufficient, so that an improvement is awaited.
Incidentally, the upper frame of the conventional stacker crane is constituted such that the pair of front and rear attachment plate for supporting the front and rear guide rollers, which are being urged to the side surface of the guide rail on the ceiling side, are connected to the left and right connecting plates, between which the front support rod is held, or to the left and right connecting plates, between which the rear support rod is held. Thus, a force acting on the guide rollers is caused when the guide rollers are guided by the guide rail; it acts on the connecting plates being connected to the support rods. Therefore, it is necessary to make the strength of the connecting plate and the strength for attaching the connecting plates to the support rods sufficiently high.